The present invention is in a method for the production of spun bonded nonwoven fabrics with improved uniformity of fleece structure and of weight per unit area distribution. The improved fleece is produced by spinning linear filament ranks disposed parallel side by side from a plurality of long spinnerets, subjecting the ranks to air jets downdraft and stretching the filaments or filament ranks by means of air streams. The spun bonded nonwoven fabric is then fixed on a moving screen.
The production of spun bonded nonwoven fabrics by mechanical or aerodynamic drawing and stretching of filaments or of filaments arrayed in ranks is known. The spun bonded nonwoven fabrics is deposited in a random structure on a moving screen and delivered in this form to a consolidating unit. When the air streams strike against the perforated conveyor belt a slight turbulence is produced during the formation of the fleece, which conflicts with and impairs the uniformity with which the fleece is laid down. It is known that the uniformity of spun bonded nonwoven fabrics can be improved especially in the case of a large number of filaments, if the filaments are spun out of long spinnerets (DE-AS No. 13 03 569). In the aerodynamic stretching of the relatively loosely guided filaments, however, there is the danger of turbulence here, too. This turbulence becomes undesirably manifest when the production of spun bonded nonwoven fabrics of low weight and high uniformity is involved.
An object of the present invention is to produce spun bonded nonwoven fabrics having a high uniformity of fleece structure and weight per unit area distribution in a manner which can be performed on a large technical scale while avoiding turbulence in the laying of the fleece. At the same time, for the reasons given above, long spinnerets are to be used, and the filament ranks disposed parallel and side by side are to be drawn and stretched aerodynamically into air jets. In the fleece-forming zone the filaments are not to become entangled on the moving screen and must not develop undesired striation and crimping. It is desirable that the method be suitable especially for large technical scale equipment processing several thousands of filaments and producing fleeces in widths of over 5 meters.